Protruding window (5)
I believe the answer is:
oriel
'protruding window' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for oriel that I've seen before include "Protruding window" , "place to study at Oxford" , "lecturer seen near Lorraine regularly" , "First-floor bay (window)" , "Recessed bay window" .)